Csbc Functions - GE Medical Systems PRODIGY Service Manual

SRAM

2.5.2 cSBC Functions

FLEX PLD Peripherals
PORT A
Bit Name
0 trans_enable
1 /trans_fwd
2 /shutter_open_ctrl
3 trans_lsw_override
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2-46 System Overview
At startup the CPU executes the boots code which programs the FLEX PLD
and then maps in either NT or Prodigy runtime firmware as appropriate based
on the most significant bit of the CCA REV register. To switch from boot code
to run code the firmware jumps to SRAM and executes a code snippet which
pages the boot code out of 0xFF and the desired firmware into 0xFF. The
snippet then jumps from SRAM back to 0xFF to execute the firmware. A boot
jumper, JP4 is provided to optionally force the CPU to remain in the boot
code. When the boot jumper is installed the boot code runs the host port at
115.2KB.
The cSBC contains a single 128K x 8 bit SRAM which provides read/write
memory. The SRAM's segments are arbitrarily mapped to any CPU segment
by the CPU mapping registers.
The microprocessor-based Single Board Controller (cSBC) provides overall
operation and control of the scan table.
The majority of scanner related programmable logic functionality is contained
in the FLEX PLD, an Altera EPF6024AQC208-3 device. Device programming
is handled exclusively by the CPU. On each cold boot the CPU reprograms
the FLEX devices from an image stored in it's FLASH. As such a firmware
download of a new FLEX image is required to permanently upgrade the PLD
code.
The functional components of the programmable logic are discussed in the
following subsections. Polarity of operation can be inferred from bit names
and use of preceding slash for inverted logic bits.
Note that ports A-F are reloaded with default values at time of CPU reset and
remain in the default state until SCANNER_RESET has been cleared and
new values are written by the firmware. Defaults for port F and all other
registers are invoked at power up only.
R/ Def. Description
W
R/W 0 Transverse motor enable – low blocks trans motor pulses and
forces Centent drive to standby current level.
R/W 0 Transverse motor direction control.
R/W 1 Shutter solenoid control.
R/W 0 Transverse limit switch override – prevent limit switch contact
from blocking step pulses at hardware level.
PRODIGY Service Manual (Rev C - 2000)